Do you? I haven't been there in a while, but the last time I was, the immigration booth is after security so you part with your bags by putting them on a belt before the preclearance process begins.

The baggage is screened for WEI and a photo of the baggag is taken; when one gets to the immigration booth, the CBPO can pull up a the photo of your checked baggage to help him decide what to do with you.

Is it still this way? If it is, are you sure the bags wouldn't be checked through and cleared this way? I have never transited YOW, but it seems silly that one would have to claim his bags only to drop it on another belt before anyone from CBP even sees it.